Porous three dimensional copper, tin, copper-tin, copper-tin-cobalt, and copper-tin-cobalt-titanium electrodes for batteries and ultra capacitors

ABSTRACT

A method and apparatus for forming a reliable and cost efficient battery or electrochemical capacitor electrode structure that has an improved lifetime, lower production costs, and improved process performance are provided. In one embodiment a method for forming a three dimensional porous electrode for a battery or an electrochemical cell is provided. The method comprises depositing a columnar metal layer over a substrate at a first current density by a diffusion limited deposition process and depositing three dimensional metal porous dendritic structures over the columnar metal layer at a second current density greater than the first current density.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/696,422, filed Jan. 29, 2010 now U.S. Pat. No. 8,206,569, whichclaims benefit of U.S. Provisional Patent Application Ser. No.61/149,933, filed Feb. 4, 2009, and is a continuation-in-part of U.S.patent application Ser. No. 12/459,313, filed Jun. 30, 2009 now U.S.Pat. No. 8,486,562, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/156,862, filed Mar. 2, 2009 and U.S. ProvisionalPatent Application Ser. No. 61/155,454, filed Feb. 25, 2009, all ofwhich are herein incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

Embodiments of the present invention generally relate to methods offorming an energy storage device. More particularly, embodimentsdescribed herein relate to methods of forming electric batteries andelectrochemical capacitors.

Description of the Related Art

Fast-charging, high-capacity energy storage devices, such assupercapacitors and lithium- (Li) ion batteries, are used in a growingnumber of applications, including portable electronics, medical,transportation, grid-connected large energy storage, renewable energystorage, and uninterruptible power supply (UPS). In modern rechargeableenergy storage devices, the current collector is made of an electricconductor. Examples of materials for the positive current collector (thecathode) include aluminum, stainless steel, and nickel. Examples ofmaterials for the negative current collector (the anode) include copper(Cu), stainless steel, and nickel (Ni). Such collectors can be in theform of a foil, a film, or a thin plate, having a thickness thatgenerally ranges from about 6 to 50 μm.

The active electrode material in the positive electrode of a Li-ionbattery is typically selected from lithium transition metal oxides, suchas LiMn₂O₄, LiCoO₂, and combinations of Ni or Li oxides and includeselectroconductive particles, such as carbon or graphite, and bindermaterial. Such positive electrode material is considered to be alithium-intercalation compound, in which the quantity of conductivematerial is in the range from 0.1% to 15% by weight.

Graphite is usually used as the active electrode material of thenegative electrode and can be in the form of a lithium-intercalationmeso-carbon micro beads (MCMB) powder made up of MCMBs having a diameterof approximately 10 μm. The lithium-intercalation MCMB powder isdispersed in a polymeric binder matrix. The polymers for the bindermatrix are made of thermoplastic polymers including polymers with rubberelasticity. The polymeric binder serves to bind together the MCMBmaterial powders to preclude crack formation and prevent disintegrationof the MCMB powder on the surface of the current collector. The quantityof polymeric binder is in the range of 2% to 30% by weight.

The separator of Li-ion batteries is typically made from micro-porouspolyethylene and polyolefin, and is applied in a separate manufacturingstep.

For most energy storage applications, the charge time and capacity ofenergy storage devices are important parameters. In addition, the size,weight, and/or expense of such energy storage devices can be significantlimitations. The use of electroconductive particles and MCMB powders andtheir associated binder materials in energy storage devices has a numberof drawbacks. Namely, such materials limit the minimum size of theelectrodes constructed from such materials, produce unfavorable internalresistance in an energy storage device, and require complex and eclecticmanufacturing methods.

Accordingly, there is a need in the art for faster charging, highercapacity energy storage devices that are smaller, lighter, and can bemore cost effectively manufactured.

SUMMARY OF THE INVENTION

Embodiments described herein generally relate to methods of forming anenergy storage device. More particularly, embodiments described hereinrelate to methods of forming electric batteries and electrochemicalcapacitors. In one embodiment a method for forming a porous electrodefor an electrochemical cell is provided. The method comprises depositinga columnar metal layer over a substrate at a first current density by adiffusion limited deposition process and depositing three dimensionalmetal porous dendritic structures over the columnar metal layer at asecond current density greater than the first current density.

In another embodiment, a method of forming a porous three dimensionalelectrode microstructure for an electrochemical cell is provided. Themethod comprises positioning a substrate in a plating solution,depositing a columnar metal layer over the substrate at a first currentdensity by a diffusion limited deposition process, and depositing porousconductive dendritic structures over the columnar metal layer at asecond current density greater than the first current density.

In yet another embodiment a battery or an electrochemical capacitor isprovided. The battery or electrochemical capacitor comprises aseparator, a collector, and a porous electrode. The porous electrodecomprises a columnar metal layer and three dimensional metal porousdendritic structures formed over the columnar metal layer.

In yet another embodiment, a substrate processing system for processinga vertically oriented flexible substrate is provided. The substrateprocessing system comprises a first plating chamber configured to platea conductive microstructure comprising a first conductive material overa portion of the vertically oriented conductive substrate, a first rinsechamber disposed adjacent to the first plating chamber configured torinse and remove any residual plating solution from the portion of thevertically oriented conductive substrate with a rinsing fluid, a secondplating chamber disposed adjacent to the first rinse chamber configuredto deposit a second conductive material over the conductivemicrostructure, a second rinse chamber disposed adjacent to the secondplating chamber configured to rinse and remove any residual platingsolution from the portion of the vertically oriented conductivesubstrate, a substrate transfer mechanism configured to transfer thevertically oriented flexible substrate among the chambers, wherein eachof the chambers comprises a processing volume, a feed roll disposedoutside the processing volume and configured to retain a portion of thevertically oriented flexible base, and a take up roll disposed outsidethe processing volume and configured to retain a portion of thevertically oriented flexible base, wherein the substrate transfermechanism is configured to activate the feed rolls and the take up rollsto move the vertically oriented flexible substrate in and out of eachchamber, and hold the vertically oriented flexible substrate in theprocessing volume of each chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1A illustrates a simplified schematic view of a lithium-ion batterycell according to embodiments described herein;

FIG. 1B illustrates a simplified schematic view of a single sided Li-ionbattery cell bi-layer electrically connected to a load according toembodiments described herein;

FIG. 2A is a flow diagram of a method for forming an anode according toembodiments described herein;

FIG. 2B is a flow diagram of a method of forming an anode according toembodiments described herein;

FIGS. 3A-3G are schematic cross-sectional views of an anode formedaccording to embodiments described herein;

FIG. 4A schematically illustrates one embodiment of a plating systemaccording to embodiments described herein;

FIG. 4B schematically illustrates one embodiment of a verticalprocessing system according to embodiments described herein;

FIG. 5 is a representation of a scanning electron microscope (SEM) imageof a three dimensionally plated electrode deposited according toembodiments described herein;

FIG. 6 is a representation of a SEM image of a three dimensionallyplated electrode deposited according to embodiments described herein;

FIGS. 7A-7D are representations of SEM images of three dimensionallyplated electrodes deposited according to embodiments described herein;and

FIG. 8 is X-ray diffraction (XRD) spectra of plated copper-tin and acopper-tin phase diagram.

To facilitate understanding, identical reference numerals have beenused, wherever possible, to designate identical elements that are commonto the figures. It is contemplated that elements and/or process steps ofone embodiment may be beneficially incorporated in other embodimentswithout additional recitation.

DETAILED DESCRIPTION

Embodiments described herein generally relate to an electrode structureuseful in a battery or an electrochemical capacitor and the methods ofcreating such an electrode structure that has an improved lifetime,lower production costs, and improved process performance. Embodimentsdescribed herein generally include a porous 3-dimensional electrodestructure with increased surface area. In one embodiment, the electrodestructure comprises a columnar metal layer and three dimensional metalporous conductive dendritic structures formed over the columnar metallayer. One embodiment described herein is a method of forming a porouselectrode structure by depositing a columnar metal layer and depositingthree dimensional metal porous dendritic structures on the columnarmetal layer by a diffusion limited electrochemical deposition processbrought on by adjusting the electrochemical process parameters, such aselectrolyte chemistry, applied voltage, applied current, and/or fluiddynamic properties at the plating surface to achieve a desireddeposition morphology.

In an effort to achieve desirable plated film morphology or filmproperties, it is often desirable to increase the concentration of metalions near the cathode (e.g., seed layer surface) by reducing thediffusion boundary layer or by increasing the metal ion concentration inthe electrolyte bath. It should be noted that the diffusion boundarylayer is strongly related to the hydrodynamic boundary layer. If themetal ion concentration is too low and/or the diffusion boundary layeris too large at a desired plating rate the limiting current (i_(L)) willbe reached. The diffusion limited plating process created when thelimiting current is reached, prevents the increase in plating rate bythe application of more power (e.g., voltage) to the cathode (e.g.,metalized substrate surface). When the limiting current is reached a lowdensity columnar film is produced due to the evolution of gas andresulting dendritic type film growth that occurs due to the masstransport limited process.

While the particular apparatus in which the embodiments described hereincan be practiced is not limited, it is particularly beneficial topractice the embodiments on a web-based roll-to-roll system sold byApplied Materials, Inc., Santa Clara, Calif. Exemplary roll-to-roll anddiscrete substrate systems on which the embodiments described herein maybe practiced are described herein and in further detail in U.S.Provisional Patent Application Ser. No. 61/243,813, titled APPARATUS ANDMETHODS FOR FORMING ENERGY STORAGE OR PV DEVICES IN A LINEAR SYSTEM andU.S. patent application Ser. No. 12/620,788, titled APPARATUS AND METHODFOR FORMING 3D NANOSTRUCTURE ELECTRODE FOR ELECTROCHEMICAL BATTERY ANDCAPACITOR, all of which are herein incorporated by reference in theirentirety.

FIG. 1A is a schematic illustration of a Li-ion battery 100 electricallyconnected to a load 109 according to embodiments described herein. Theprimary functional components of Li-ion battery 100 include a currentcollector 101, an anode structure 102, a cathode structure 103, aseparator 104, and an electrolyte (not shown). The electrolyte iscontained in anode structure 102, cathode structure 103, and separator104, and a variety of materials may be used as electrolyte, such as alithium salt in an organic solvent. In operation, Li-ion battery 100provides electrical energy, i.e., is discharged, when anode structure102 and cathode structure 103 are electrically coupled to load 109, asshown in FIG. 1A. Electrons flow from current collector 101 through load109 to current collector 113 of cathode structure 103, and lithium ionsmove from the anode structure 102, through separator 104, and intocathode structure 103.

FIG. 1B is a schematic diagram of a single sided Li-ion battery cellbi-layer 120 with anode structures 122 a, 122 b electrically connectedto a load 121, according to one embodiment described herein. The singlesided Li-ion battery cell bi-layer 120 functions similarly to the Li-ionbattery 100 depicted in FIG. 1A. The primary functional components ofLi-ion battery cell bi-layer 120 include anode structures 122 a, 122 b,cathode structures 123 a, 123 b, separator layers 124 a, 124 b, and anelectrolyte (not shown) disposed within the region between the currentcollectors 131 a, 131 b, 133 a, and 133 b. The Li-ion battery cell 120is hermetically sealed with electrolyte in a suitable package with leadsfor the current collectors 131 a, 131 b, 133 a, and 133 b. The anodestructures 122 a, 122 b, cathode structures 123 a, 123 b, andfluid-permeable separator layers 124 a, 124 b are immersed in theelectrolyte in the region formed between the current collectors 131 aand 133 a and the region formed between the current collectors 131 b and133 b. An insulator layer 135 is disposed between current collector 133a and current collector 133 b.

Anode structures 122 a, 122 b and cathode structures 123 a, 123 b eachserve as a half-cell of Li-ion battery cell 120, and together form acomplete working bi-layer cell of Li-ion battery 120. Anode structures122 a, 122 b each include a metal current collector 131 a, 131 b and afirst electrolyte containing material 134 a, 134 b. Similarly, cathodestructures 123 a, 123 b include a current collector 133 a and 133 brespectively and a second electrolyte containing material 132 a, 132 b,such as a metal oxide, for retaining lithium ions. The currentcollectors 131 a, 131 b, 133 a, and 133 b are made of electricallyconductive material such as metals. In some cases, a separator layer 124a, 124 b, which is an insulating, porous, fluid-permeable layer, forexample, a dielectric layer, may be used to prevent direct electricalcontact between the components in the anode structures 122 a, 122 b andthe cathode structures 123 a, 123 b.

The electrolyte containing porous material on the cathode side of theLi-ion battery 100, or positive electrode, may comprise alithium-containing metal oxide, such as lithium cobalt dioxide (LiCoO₂)or lithium manganese dioxide (LiMnO₂). The electrolyte containing porousmaterial may be made from a layered oxide, such as lithium cobalt oxide,an olivine, such as lithium iron phosphate, or a spinel, such as lithiummanganese oxide. In non-lithium embodiments, an exemplary cathode may bemade from TiS₂ (titanium disulfide). Exemplary lithium-containing oxidesmay be layered, such as lithium cobalt oxide (LiCoO₂), or mixed metaloxides, such as LiNi_(x)Co_(1-2x)MnO₂, LiNi_(0.5)Mn_(1.5)O₄,Li(Ni_(0.8)Co_(0.15)Al_(0.05))O₂, LiMn₂O₄. Exemplary phosphates may beiron olivine (LiFePO₄) and it is variants (such as LiFe_(1-x)MgPO₄),LiMoPO₄, LiCoPO₄, LiNiPO₄, Li₃V₂(PO₄)₃, LiVOPO₄, LiMP₂O₇, orLiFe_(1.5)P₂O₇. Exemplary fluorophosphates may be LiVPO₄F, LiAlPO₄F,Li₅V(PO₄)₂F₂, Li₅Cr(PO₄)₂F₂, Li₂CoPO₄F, or Li₂NiPO₄F. Exemplarysilicates may be Li₂FeSiO₄, Li₂MnSiO₄, or Li₂VOSiO₄. An exemplarynon-lithium compound is Na₅V₂(PO₄)₂F₃.

The electrolyte containing porous material on the anode side of theLi-ion battery 100, or negative electrode, may be made from materialsdescribed above, for example, graphitic particles dispersed in a polymermatrix and/or various fine powders, for example, micro-scale ornano-scale sized powders. Additionally, microbeads of silicon, tin, orlithium titanate (Li₄Ti₅O₁₂) may be used with, or instead of, graphiticmicrobeads to provide the conductive core anode material. It should alsobe understood that the embodiments described herein are not limited tothe Li-ion battery cells depicted in FIGS. 1A and 1B. It should also beunderstood, that the anode structures and the cathode structures may beconnected either in series or in parallel.

FIG. 2A is a flow diagram according to one embodiment described hereinof a process 200 for forming a porous three dimensional conductiveelectrode in accordance with embodiments described herein. FIGS. 3A-3Fare schematic cross-sectional views of a porous three dimensionalconductive electrode formed according to embodiments described herein.The process 200 includes process steps 202-212, wherein a porouselectrode is formed on a substrate 300. In one embodiment, the process200 may be performed as a roll-to-roll manufacturing process. The firstprocess step 202 includes providing the substrate 300. In oneembodiment, the substrate 300 may comprise a material selected from thegroup comprising or consisting of copper, aluminum, nickel, zinc, tin,titanium, flexible materials, stainless steel, and combinations thereof.In one embodiment, the substrate 300 is a flexible substrate comprisinga material selected from the group comprising or consisting of copper,aluminum, nickel, zinc, tin, stainless steel, and combinations thereof.In one embodiment, the substrate is a copper foil substrate. In oneembodiment, the substrate 300 has layers deposited thereon. In oneembodiment, the layers are selected from the group comprising orconsisting of copper, titanium, chromium, alloys thereof, andcombinations thereof.

Flexible substrates can be constructed from polymeric materials, such asa polyimide (e.g., KAPTON™ by DuPont Corporation),polyethyleneterephthalate (PET), polyacrylates, polycarbonate, silicone,epoxy resins, silicone-functionalized epoxy resins, polyester (e.g.,MYLAR™ by E.I. du Pont de Nemours & Co.), APICAL AV manufactured byKanegaftigi Chemical Industry Company, UPILEX manufactured by UBEIndustries, Ltd.; polyethersulfones (PES) manufactured by Sumitomo, apolyetherimide (e.g., ULTEM by General Electric Company), andpolyethylenenaphthalene (PEN). In some cases the substrate can beconstructed from a metal foil, such as stainless steel that has aninsulating coating disposed thereon. Alternately, flexible substrate canbe constructed from a relatively thin glass that is reinforced with apolymeric coating.

In one embodiment, the substrate may be roughened by chemically treatingthe surface of the substrate to increase the surface area.

The second process step 204 includes optionally depositing a barrierlayer and/or adhesion layer 302 over the substrate. The barrier layer302 may be deposited to prevent or inhibit diffusion of subsequentlydeposited materials over the barrier layer into the underlyingsubstrate. In one embodiment the barrier layer comprises multiple layerssuch as a barrier-adhesion layer or an adhesion-release layer. Examplesof barrier layer materials include refractory metals and refractorymetal nitrides such as chromium, tantalum (Ta), tantalum nitride(TaN_(x)), titanium (Ti), titanium nitride (TiN_(x)), tungsten (W),tungsten nitride (WN_(x)), alloys thereof, and combinations thereof.Other examples of barrier layer materials include PVD titanium stuffedwith nitrogen, doped silicon, aluminum, aluminum oxides, titaniumsilicon nitride, tungsten silicon nitride, and combinations thereof.Exemplary barrier layers and barrier layer deposition techniques arefurther described in U.S. Patent Application Publication 2003/0143837entitled “Method of Depositing A Catalytic Seed Layer,” filed on Jan.28, 2002, which is incorporated herein by reference to the extent notinconsistent with the embodiments described herein.

The barrier layer may be deposited by CVD techniques, PVD techniques,electroless deposition techniques, evaporation, or molecular beamepitaxy. The barrier layer may also be a multi-layered film depositedindividually or sequentially by the same or by a combination oftechniques.

Physical vapor deposition techniques suitable for the deposition of thebarrier layer include techniques such as high density plasma physicalvapor deposition (HDP PVD) or collimated or long throw sputtering. Onetype of HDP PVD is ionized metal plasma physical vapor deposition (IMPPVD). An example of a chamber capable of IMP PVD of a barrier layer isan IMP VECTRA™ chamber. The chamber and process regime are availablefrom Applied Materials, Inc. of Santa Clara, Calif. Generally, IMP PVDinvolves ionizing a significant fraction of material sputtered from ametal target to deposit a layer of the sputtered material on asubstrate. Power supplied to a coil in the chamber enhances theionization of the sputtered material. The ionization enables thesputtered material to be attracted in a substantially perpendiculardirection to a biased substrate surface and to deposit a layer ofmaterial with good step coverage over high aspect ratio features. Thechamber may also include a reactive processing gas, such as nitrogen forthe deposition of a metal nitride. An exemplary process for thedeposition of barrier layers utilizing physical vapor deposition is morefully described in co-pending U.S. patent application Ser. No.09/650,108, entitled, “Method For Achieving Copper Fill Of High AspectRatio Interconnect Features,” filed on Aug. 29, 2000, issued as U.S.Pat. No. 6,436,267 which is incorporated herein by reference to theextent not inconsistent with the invention.

An example of a chamber capable of chemical vapor deposition of abarrier layer is a CVD TxZ™ chamber. The chamber and the process regimeare available from Applied Materials, Inc. of Santa Clara, Calif.Generally, chemical vapor deposition involves flowing a metal precursorinto the chamber. The metal precursor chemically reacts to deposit ametal film on the substrate surface. Chemical vapor deposition mayfurther include utilizing a plasma to aid in the deposition of the metalfilm on the substrate surface. Exemplary processes for the deposition ofbarrier layers from metal precursors are more fully described inco-pending U.S. patent application Ser. No. 09/505,638, entitled,“Chemical Vapor Deposition of Barriers From Novel Precursors,” filed onFeb. 16, 2000, issued as U.S. Pat. No. 6,743,473 on Jun. 1, 2004, and inU.S. patent application Ser. No. 09/522,726, entitled, “MOCVD ApproachTo Deposit Tantalum Nitride Layers,” filed on Mar. 10, 2000, bothincorporated herein by reference to the extent not inconsistent with theinvention. In addition, the PVD chamber and/or the CVD chamber can beintegrated into a processing platform, such as an ENDURA™ platform, alsoavailable from Applied Materials, Inc. of Santa Clara, Calif.

An example of a processing tool capable of roll-to-roll evaporation of abarrier layer is the SMARTWEB™ vacuum web coater available from AppliedMaterials, Inc. of Santa Clara, Calif. Generally evaporation involvesplacing the material to be deposited or source material in a chamber orcrucible and heating in a vacuum environment until the materialvaporizes. One method of heating involves using an electron beam to heatthe material. The use of a high vacuum environment increases the meanfree path of the vapor molecules allowing the vapor to travel in astraight path with minimal collisions until the vapor strikes a surfaceand condenses to form a film. The rate of removal from the sourcematerial varies with vapor pressure which correspondingly varies withtemperature. For example, as the vapor pressure increases whichgenerally corresponds to an increase in temperature, the rate of removalfrom the source material also increases. Films which may be depositedusing evaporation methods include films containing Copper (Cu), Chromium(Cr), Titanium (Ti), alloys thereof, combinations thereof, and TitaniumNitride (TiN).

The third process step 206 includes optionally depositing a seed layer304 over the substrate 300. The seed layer 304 comprises a conductivemetal that aids in subsequent deposition of materials thereover. Theseed layer 304 preferably comprises a copper seed layer or alloysthereof. Other metals, particularly noble metals, may also be used forthe seed layer. The seed layer 304 may be deposited over the barrierlayer by techniques conventionally known in the art including physicalvapor deposition techniques, chemical vapor deposition techniques, andelectroless deposition techniques.

Physical vapor deposition techniques suitable for the deposition of theseed layer include techniques such as high density plasma physical vapordeposition (HDP PVD) or collimated or long throw sputtering. One type ofHDP PVD is ionized metal plasma physical vapor deposition (IMP PVD). Anexample of a chamber capable of ionized metal plasma physical vapordeposition of a seed layer is an IMP Vectra™ chamber. The chamber andprocess regime are available from Applied Materials, Inc. of SantaClara, Calif. An exemplary process for the deposition of a seed layerutilizing PVD techniques is more fully described in co-pending U.S.patent application Ser. No. 09/650,108, entitled, “Method For AchievingCopper Fill of High Aspect Ratio Interconnect Features,” filed on Aug.29, 2000, which is incorporated herein by reference to the extent notinconsistent with the invention. An example of a chamber capable ofchemical vapor deposition of the seed layer is a CVD TxZ™ chamber. Thechamber and the process regime are also available from AppliedMaterials, Inc. of Santa Clara, Calif. An exemplary process for thedeposition of a seed layer utilizing CVD techniques is more fullydescribed in U.S. Pat. No. 6,171,661 entitled “Deposition of Copper WithIncreased Adhesion,” issued on Jan. 9, 2001.

The fourth process step 208 includes forming a columnar metal layer 306over the seed layer 304. In certain embodiments, the columnar metallayer 306 is formed directly on a surface of the substrate 300.Formation of the columnar metal layer 306 includes establishing processconditions under which evolution of hydrogen results in the formation ofa porous metal film. In one embodiment, such process conditions areachieved by performing at least one of: increasing the concentration ofmetal ions near the cathode (e.g., seed layer surface) by reducing thediffusion boundary layer, and by increasing the metal ion concentrationin the electrolyte bath. It should be noted that the diffusion boundarylayer is strongly related to the hydrodynamic boundary layer. If themetal ion concentration is too low and/or the diffusion boundary layeris too large at a desired plating rate the limiting current (i_(L)) willbe reached. The diffusion limited plating process created when thelimiting current is reached, prevents the increase in plating rate bythe application of more power (e.g., voltage) to the cathode (e.g.,metalized substrate surface). When the limiting current is reached a lowdensity columnar metal layer 306 is produced due to the evolution of gasand resulting dendritic type film growth that occurs due to the masstransport limited process.

Plating Solutions:

Formation of the columnar metal layer 306 generally takes place in aprocessing chamber. A processing chamber that may be adapted to performone or more of the process steps described herein may include anelectroplating chamber, such as the SLIMCELL® electroplating chamberavailable from Applied Materials, Inc. of Santa Clara, Calif. Otherprocessing chambers and systems, including those available from othermanufactures may also be used to practice the embodiments describedherein. One exemplary processing system includes a roll-to-rollprocessing system described herein.

The processing chamber includes a suitable plating solution. Suitableplating solutions that may be used with the processes described hereininclude electrolyte solutions containing a metal ion source, an acidsolution, and optional additives.

In one embodiment, to increase planarization power, the plating solutionused in step 208 contains at least one or more acid solutions. Suitableacid solutions include, for example, inorganic acids such as sulfuricacid, phosphoric acid, pyrophosphoric acid, perchloric acid, aceticacid, citric acid, combinations thereof, as well as acid electrolytederivatives, including ammonium and potassium salts thereof.

Optionally, the plating solution may include one or more additivecompounds. Additive compounds include electrolyte additives including,but not limited to, suppressors, enhancers, levelers, brighteners andstabilizers to improve the effectiveness of the plating solution fordepositing metal, namely copper to the substrate surface. For example,certain additives may be used to control the mechanism of bubbleformation. Certain additives may decrease the ionization rate of themetal atoms, thereby inhibiting the dissolution process, whereas otheradditives may provide a finished, shiny substrate surface. The additivesmay be present in the plating solution in concentrations up to about 15%by weight or volume, and may vary based upon the desired result afterplating. Optional additives include polyethylene glycol (PEG),polyethylene glycol derivatives, polyamides, polyimides includingpolyethyleneimide, polyglycine, 2-amino-1-napthalenesulfonic acid,3-amino-1-propane-sulfonic acid, 4-aminotoluene-2-sulfonic acid,polyacrylamide, polyacrylic acid polymers, polycarboxylate copolymers,coconut diethanolamide, oleic diethanolamide, ethanolamide derivatives,sulfur containing compounds such as sulfite or di-sulfite, andcombinations thereof.

In one embodiment, the metal ion source within the plating solution usedin step 208 is a copper ion source. In one embodiment, the concentrationof copper ions in the electrolyte may range from about 0.1 M to about1.1M, preferably from about 0.4 M to about 0.9 M. Useful copper sourcesinclude copper sulfate (CuSO₄), copper chloride (CuCl₂), copper acetate(Cu(CO₂CH₃)₂), copper pyrophosphate (Cu₂P₂O₇), copper fluoroborate(Cu(BF₄)₂), derivatives thereof, hydrates thereof or combinationsthereof. The electrolyte composition can also be based on the alkalinecopper plating baths (e.g., cyanide, glycerin, ammonia, etc) as well.

In one example, the electrolyte is an aqueous solution that containsbetween about 200 and 250 g/l of copper sulfate pentahydrate(CuSO₄.5(H₂O)), between about 40 and about 70 g/l of sulfuric acid(H₂SO₄), and about 0.04 g/l of hydrochloric acid (HCl). In some cases itis desirable to add a low cost pH adjusting agent, such as potassiumhydroxide (KOH) or sodium hydroxide (NaOH) to form an inexpensiveelectrolyte that has a desirable pH to reduce the cost of ownershiprequired to form a metal contact structure for a solar cell. In somecases it is desirable to use tetramethylammonium hydroxide (TMAH) toadjust the pH.

In another example, the electrolyte is an aqueous solution that containsbetween about 220 and 250 g/l of copper fluoroborate (Cu(BF₄)₂), betweenabout 2 and about 15 g/l of tetrafluoroboric acid (HBF₄), and about 15and about 16 g/l of boric acid (H₃BO₃). In some cases it is desirable toadd a pH adjusting agent, such as potassium hydroxide (KOH), or sodiumhydroxide (NaOH) to form an inexpensive electrolyte that has a desirablepH to reduce the cost of ownership required to form a metal contactstructure for a solar cell. In some cases it is desirable to usetetramethylammonium hydroxide (TMAH) to adjust the pH.

In yet another example, the electrolyte is an aqueous solution thatcontains between about 60 and about 90 g/l of copper sulfatepentahydrate (CuSO₄.5(H₂O)), between about 300 and about 330 g/l ofpotassium pyrophosphate (K₄P₂O₇), and about 10 to about 35 g/l of5-sulfosalicylic acid dehydrate sodium salt (C₇H₅O₆SNa.2H₂O). In somecases it is desirable to add a pH adjusting agent, such as potassiumhydroxide (KOH), or sodium hydroxide (NaOH) to form an inexpensiveelectrolyte that has a desirable pH to reduce the cost of ownershiprequired to form a metal contact structure for a solar cell. In somecases it is desirable to use tetramethylammonium hydroxide (TMAH) toadjust the pH.

In yet another embodiment, the electrolyte is an aqueous solution thatcontains between about 30 and about 50 g/l of copper sulfatepentahydrate (CuSO₄.5(H₂O)), and between about 120 and about 180 g/l ofsodium pyrophosphate decahydrate (Na₄P₂O₇.10(H₂O)). In some cases it isdesirable to add a pH adjusting agent, such as potassium hydroxide(KOH), or sodium hydroxide (NaOH) to form an inexpensive electrolytethat has a desirable pH to reduce the cost of ownership required to forma metal contact structure for a solar cell. In some cases it isdesirable to use tetramethylammonium hydroxide (TMAH) to adjust the pH.

In one embodiment, it may be desirable to add a second metal ion to theprimary metal ion containing electrolyte bath (e.g., copper ioncontaining bath) that will plate out or be incorporated in the growingelectrochemically deposited layer or on the grain boundaries of theelectrochemically deposited layer. The formation of a metal layer thatcontains a percentage of a second element can be useful to reduce theintrinsic stress of the formed layer and/or improve its electrical andelectromigration properties. In one example, it is desirable to add anamount of a silver (Ag), nickel (Ni), zinc (Zn), tin (Sn), or lithium(Li) metal ion source to a copper plating bath to form a copper alloythat has between about 1% and about 4% of the second metal in thedeposited layer.

In one example, the metal ion source within the electrolyte solutionused in step 208 is a silver, tin, zinc or nickel ion source. In oneembodiment, the concentration of silver, tin, zinc or nickel ions in theelectrolyte may range from about 0.1 M to about 0.4M. Useful nickelsources include nickel sulfate, nickel chloride, nickel acetate, nickelphosphate, derivatives thereof, hydrates thereof or combinationsthereof.

Examples of suitable tin sources include soluble tin compounds. Asoluble tin compound can be a stannic or stannous salt. The stannic orstannous salt can be a sulfate, an alkane sulfonate, or an alkanolsulfonate. For example, the bath soluble tin compound can be one or morestannous alkane sulfonates of the formula:(RSO₃)₂Snwhere R is an alkyl group that includes from one to twelve carbon atoms.The stannous alkane sulfonate can be stannous methane sulfonate with theformula:

The bath soluble tin compound can also be stannous sulfate of theformula: SnSO₄

Examples of the soluble tin compound can also include tin(II) salts oforganic sulfonic acid such as methanesulfonic acid, ethanesulfonic acid,2-propanolsulfonic acid, p-phenolsulfonic acid and like, tin(II)borofluoride, tin(II) sulfosuccinate, tin(II) sulfate, tin(II) oxide,tin(II) chloride and the like. These soluble tin(II) compounds may beused alone or in combination of two or more kinds.

Example of suitable cobalt source may include cobalt salt selected fromcobalt sulfate, cobalt nitrate, cobalt chloride, cobalt bromide, cobaltcarbonate, cobalt acetate, ethylene diamine tetraacetic acid cobalt,cobalt (II) acetyl acetonate, cobalt (III) acetyl acetonate, glycinecobalt (III), and cobalt pyrophosphate, or combinations thereof.

In one embodiment, the plating solution contains free copper ions inplace of copper source compounds and complexed copper ions.

The columnar metal layer 306 is formed using a diffusion limiteddeposition process. The current densities of the deposition bias areselected such that the current densities are above the limiting current(i_(L)). When the limiting current is reached the columnar metal film isformed due to the evolution of hydrogen gas and resulting dendritic typefilm growth that occurs due to the mass transport limited process.During formation of the columnar metal layer, the deposition biasgenerally has a current density of about 10 A/cm² or less, preferablyabout 5 A/cm² or less, more preferably at about 3 A/cm² or less. In oneembodiment, the deposition bias has a current density in the range fromabout 0.05 A/cm² to about 3.0 A/cm². In another embodiment, thedeposition bias has a current density between about 0.1 A/cm² and about0.5 A/cm². In yet another embodiment, the deposition bias has a currentdensity between about 0.05 A/cm² and about 0.3 A/cm². In yet anotherembodiment, the deposition bias has a current density between about 0.05A/cm² and about 0.2 A/cm². In one embodiment, this results in theformation of a columnar metal layer between about 1 micron and about 300microns thick on the copper seed layer. In another embodiment, thisresults in the formation of a columnar metal layer between about 10microns and about 30 microns. In yet another embodiment, this results inthe formation of a columnar metal layer between about 30 microns andabout 100 microns. In yet another embodiment, this results in theformation of a columnar metal layer between about 1 micron and about 10microns, for example, about 5 microns.

In one embodiment, the columnar metal layer 306 may be deposited using amulti-step plating process. For example, the multi-step plating processmay use different current densities for each step.

The fifth process step 210 includes forming porous conductive dendriticstructure 308 on the columnar metal layer 306. The porous conductivedendritic structure 308 may be formed on the columnar metal layer 306 byincreasing the voltage and corresponding current density from thedeposition of the columnar metal layer. The deposition bias generallyhas a current density of about 10 A/cm² or less, preferably about 5A/cm² or less, more preferably at about 3 A/cm² or less. In oneembodiment, the deposition bias has a current density in the range fromabout 0.3 A/cm² to about 3.0 A/cm². In another embodiment, thedeposition bias has a current density in the range of about 1 A/cm² andabout 2 A/cm². In yet another embodiment, the deposition bias has acurrent density in the range of about 0.5 A/cm² and about 2 A/cm². Inyet another embodiment, the deposition bias has a current density in therange of about 0.3 A/cm² and about 1 A/cm². In yet another embodiment,the deposition bias has a current density in the range of about 0.3A/cm² and about 2 A/cm². In one embodiment, the porous conductivedendritic structure 308 has a porosity of between 30% and 70%, forexample, about 50%, of the total surface area.

In one embodiment, the porous conductive dendritic structure 308 maycomprise one or more of various forms of porosities. In one embodiment,the porous conductive dendritic structure 308 comprises a macro-porousdendritic structure having pores of about 100 microns or less, whereinthe non-porous portion of the macro-porous dendritic structure has poresof between about 2 nm to about 50 nm in diameter (meso-porosity). Inanother embodiment, the porous dendritic structure 308 comprises amacro-porous dendritic structure having pores of about 30 microns.Additionally, surfaces of the porous dendritic structure 308 maycomprise nano-structures. The combination of micro-porosity,meso-porosity, and nano structure yields a significant increase in thesurface area of the porous dendritic structure 308.

In one embodiment, the porous dendritic structure 308 may be formed froma single material, such as copper, zinc, nickel, cobalt, palladium,platinum, tin, ruthenium, lithium, and other suitable material. Inanother embodiment, the porous dendritic structure 308 may comprisealloys of copper, zinc, nickel, cobalt, palladium, platinum, tin,ruthenium, lithium, combinations thereof, or other suitable materials.In one embodiment, the porous dendritic structure 308 comprises acopper-tin alloy.

Optionally, a sixth processing step 212 can be performed to form anadditional layer or passivation layer 310 on the porous dendriticstructure 308, as shown in FIG. 3F. In one embodiment, the passivationlayer 310 has a thickness between about 1 nm and about 1000 nm. Inanother embodiment, the passivation layer 310 has a thickness betweenabout 200 nm and about 800 nm. In yet another embodiment, thepassivation layer 310 has a thickness between about 400 nm and about 600nm. In one embodiment, the passivation layer 310 is a copper containinglayer selected from the group comprising copper oxides (Cu₂O, CuO,Cu₂O—CuO), copper-chlorides (CuCl), copper-sulfides (Cu₂S, CuS,Cu₂S—CuS), copper-nitriles, copper-carbonates, copper-phosphides,copper-tin oxides, copper-cobalt-tin oxides, copper-cobalt-tin-titaniumoxides, copper-silicon oxides, copper-nickel oxides, copper-cobaltoxides, copper-cobalt-tin-titanium oxides, copper-cobalt-nickel-aluminumoxides, copper-titanium oxides, copper-manganese oxides, and copper-ironphosphates. In one embodiment, the passivation layer 310 is an aluminumcontaining layer such as an aluminum-silicon layer. In one embodiment,the passivation layer 310 is a lithium containing layer selected fromthe group comprising lithium-copper-phosphorous-oxynitride (P—O—N),lithium-copper-boron-oxynitride (B—O—N), lithium-copper-oxides,lithium-copper-silicon oxides, lithium-copper-nickel oxides,lithium-copper-tin oxides, lithium-copper-cobalt oxides,lithium-copper-cobalt-tin-titanium oxides,lithium-copper-cobalt-nickel-aluminum oxides, lithium-copper-titaniumoxides, lithium-aluminum-silicon, lithium-copper-manganese oxides, andlithium-copper-iron-phosphides. In one embodiment, lithium is insertedinto the lithium containing layers after the first charge. In anotherembodiment, lithium is inserted into the passivation layer by exposingthe passivation layer to a lithium containing solution. In oneembodiment, lithium is deposited using a plasma spraying process.

In one embodiment, the additional structures or layers 310 may comprisea metal or metal alloy layer. The layer 310 may comprise a materialselected from the group consisting of tin, cobalt, and combinationsthereof. The layer 310 can be formed by an electrochemical platingprocess. The layer 310 provides high capacity and long cycle life forthe electrode to be formed. In one embodiment, the porous structure 308comprises copper and tin alloy and the layer 310 comprises a tin layer.In another embodiment, the porous structure 308 comprises cobalt and atin alloy. In one embodiment, the layer 310 may be formed by immersingthe substrate 300 in a new plating bath configured to plate the layer310 after a rinsing step.

The electrode structure can be of any shape (e.g., circular, square,rectangle, polygonal, etc.) and size. Also, the type of electrodematerial is not limiting and can be made of any material that isconductive or that can be made conductive, such as a metal, plastic,graphite, polymers, carbon-containing polymer, composite, or othersuitable materials. More specifically, the electrode material maycomprise, for example, copper, zinc, nickel, cobalt, palladium,platinum, tin, ruthenium, stainless steel, alloys thereof, andcombinations thereof. In one embodiment, it is desirable to form anelectrode out of a light weight and inexpensive plastic material, suchas polyethylene, polypropylene or other suitable plastic or polymericmaterial.

Optionally, a seventh processing step can be performed to anneal thesubstrate. During the annealing process, the substrate may be heated toa temperature in a range from about 100° C. to about 250° C., forexample, between about 150° C. and about 190° C. Generally, thesubstrate may be annealed in an atmosphere containing at least oneanneal gas, such as O₂, N₂, NH₃, N₂H₄, NO, N₂O, or combinations thereof.In one embodiment, the substrate may be annealed in ambient atmosphere.The substrate may be annealed at a pressure from about 5 Torr to about100 Torr, for example, at about 50 Torr. In certain embodiments, theannealing process serves to drive out moisture from the pore structure.In certain embodiments, the annealing process serves to diffuse atomsinto the copper base, for example, annealing the substrate allows tinatoms to diffuse into the copper base, making a much stronger copper-tinlayer bond.

FIG. 2B is a flow diagram of a method 220 of forming an anode accordingto embodiments described herein. FIG. 3G is a schematic cross-sectionalview of an electrode 320 similar to electrode formed according to theembodiments described in FIG. 2B. At box 222, a columnar metal layer 326similar to columnar metal layer 306 is formed over a copper foilsubstrate 324. At box 224, a three-dimensional porous dendriticstructure 328 similar to three dimensional porous dendritic structure308 is formed over the copper foil substrate 324.

Certain embodiments described herein further include lithiatedelectrodes and processes for forming lithiated electrodes by theapplication of a pre-lithiation process to the electrodes describedherein. In one embodiment, the pre-lithiation process may be performedby adding a lithium source to the aforementioned plating solutions.Suitable lithium sources include but are not limited to LiH₂PO₄, LiOH,LiNO₃, LiCH₃COO, LiCl, Li₂SO₄, Li₃PO₄, Li(C₅H₈O₂), lithium surfacestabilized particles (e.g. carbon coated lithium particles), andcombinations thereof. The pre-lithiation process may further compriseadding a complexing agent, for example, citric acid and salts thereof tothe plating solution. In one embodiment, the pre-lithiation processresults in an electrode comprising about 1-40 atomic percent lithium. Inanother embodiment, the pre-lithiation process results in an electrodecomprising about 10-25 atomic percent lithium.

In certain embodiments, the pre-lithiation process may be performed byapplying lithium to the electrode in a particle form using powderapplication techniques including but not limited to sifting techniques,electrostatic spraying techniques, thermal or flame spraying techniques,fluidized bed coating techniques, slit coating techniques, roll coatingtechniques, and combinations thereof, all of which are known to thoseskilled in the art.

EXAMPLES

The following hypothetical non-limiting examples are provided to furtherillustrate embodiments described herein. However, the examples are notintended to be all inclusive and are not intended to limit the scope ofthe embodiments described herein.

Copper Example #1

A substrate was placed in an electroplating chamber comprising a Pt(Ti)anode with a surface area of about 3 cm². A three dimensional porouscopper electrode was formed in a plating solution initially comprising1.0 M sulfuric acid, 0.28 M copper sulfate, and 200 ppm of citric acid.A columnar copper structure was deposited at a current density of about0.4 A/cm². Three dimensional porous copper structures were deposited onthe columnar metal layer at a current density of about 1.3 A/cm². Theprocess was performed at room temperature.

Example #2

A substrate was placed in an electroplating chamber comprising a Pt(Ti)anode with a surface area of about 25 cm². A three dimensional porouscopper electrode was formed in a plating solution initially comprising1.0 M sulfuric acid, 0.28 M copper sulfate, and 200 ppm of citric acid.A columnar copper structure was deposited at a current density of about0.5 A/cm². Three dimensional copper porous dendritic structures weredeposited on the columnar copper structure at a current density of about1.5 A/cm². The process was performed at room temperature.

Example #3

A substrate was placed in an electroplating chamber comprising a Pt(Ti)anode with a surface area of about 1 m². A three dimensional copperporous electrode was formed in a plating solution initially comprising1.0 M sulfuric acid, 0.28 M copper sulfate, and 200 ppm of citric acid.A columnar copper structure was deposited at a current density of about0.5 A/cm². Three dimensional porous dendritic structures were depositedon the columnar copper structure at a current density of about 1.7A/cm². The process was performed at room temperature.

Example #4

A substrate was placed in an electroplating chamber comprising a Pt(Ti)anode with a surface area of about 1 m². A three dimensional porouscopper electrode was formed in a plating solution initially comprising1.0 M sulfuric acid, 0.28 M copper sulfate, and 200 ppm of citric acid.A columnar copper structure was deposited at a current density of about0.1 A/cm². Three dimensional porous copper dendritic structures weredeposited on the columnar copper structure at a current density of about1.5 A/cm². The process was performed at room temperature.

Example #5

A substrate was placed in an electroplating chamber comprising a Pt(Ti)anode with a surface area of about 25 cm². A three dimensional porouscopper electrode was formed in a plating solution initially comprising1.0 M sulfuric acid, 0.28 M copper sulfate, and 200 ppm of citric acid.A columnar copper structure was deposited at a current density of about0.4 A/cm². Three dimensional copper porous dendritic structures weredeposited on the columnar porous dendritic structure at a currentdensity of about 2 A/cm². The process was performed at room temperature.

Tin Example #6

A substrate was placed in an electroplating chamber comprising a Pt(Ti)anode with a surface area of about 25 cm². A three dimensional porouselectrode was formed in a plating solution initially comprising 1.0 Msulfuric acid, 0.25 M stannous sulfate, and 200 ppm of citric acid. Acolumnar tin structure was deposited at a current density of about 0.05A/cm². Three dimensional porous tin structures were deposited on thecolumnar tin structure at a current density of about 2 A/cm². Theprocess was performed at room temperature.

Example #7

A substrate was placed in an electroplating chamber comprising a Pt(Ti)anode with a surface area of about 1 m². A three dimensional porous tinelectrode was formed in a plating solution initially comprising 1.0 Msulfuric acid, 0.25 M stannous sulfate, and 200 ppm of citric acid. Acolumnar tin structure was deposited at a current density of about 0.3A/cm². Three dimensional porous tin structures were deposited on thecolumnar tin structure at a current density of about 1.5 A/cm². Theprocess was performed at room temperature.

Copper-Tin Example #8

A substrate was placed in an electroplating chamber comprising a Pt(Ti)anode with a surface area of about 25 cm². A three dimensional porouscopper-tin electrode was formed in a plating solution initiallycomprising 1.0 M sulfuric acid, 0.28 M copper sulfate, 0.15 M stannoussulfate, and 200 ppm of citric acid. A columnar copper-tin alloystructure was deposited at a current density of about 0.1 A/cm². Threedimensional copper-tin alloy porous dendritic structures were depositedon the columnar copper-tin alloy structure at a current density of about1.0 A/cm². The process was performed at room temperature.

Example #9

A substrate was placed in an electroplating chamber comprising a Pt(Ti)anode with a surface area of about 3 cm². A three dimensional copper-tinporous electrode structure was formed in a plating solution initiallycomprising 1.0 M sulfuric acid, 0.28 M copper sulfate, 0.23 M stannoussulfate, and 200 ppm of citric acid. A columnar copper-tin structure wasdeposited at a current density of about 0.2 A/cm². Three dimensionalporous copper-tin structures were deposited on the columnar copper-tinstructure at a current density of about 1.0 A/cm². The process wasperformed at room temperature.

Copper-Tin-Cobalt Titanium Example #10

A substrate comprising a titanium layer was placed in an electroplatingchamber comprising a Pt(Ti) anode with a surface area of about 25 cm². Athree dimensional copper-tin-cobalt porous electrode was formed in aplating solution initially comprising 1.0 M sulfuric acid, 0.28 M coppersulfate, 0.17 M stannous sulfate, 0.15 cobalt sulfate, and 200 ppm ofcitric acid. A columnar copper-tin-cobalt structure was deposited at acurrent density of about 0.06 A/cm². Three dimensional copper-tin-cobaltporous dendritic structures were deposited on the columnarcopper-tin-cobalt structure at a current density of about 0.3 A/cm². Theprocess was performed at room temperature.

Example #11

A substrate comprising a titanium layer was placed in an electroplatingchamber comprising a Pt(Ti) anode with a surface area of about 25 cm². Athree dimensional copper-tin-cobalt porous electrode was formed in aplating solution initially comprising 1.0 M sulfuric acid, 0.28 M coppersulfate, 0.23 M stannous sulfate, 0.21 cobalt sulfate, and 200 ppm ofcitric acid. A columnar copper-tin-cobalt structure was deposited at acurrent density of about 0.3 A/cm². Three dimensional copper-tin-cobaltporous dendritic structures were deposited on the columnarcopper-tin-cobalt structure at a current density of about 1.5 A/cm². Theprocess was performed at room temperature.

Example #12

A substrate comprising a titanium layer was placed in an electroplatingchamber comprising a Pt(Ti) anode with a surface area of about 3 cm². Athree dimensional copper-tin-cobalt porous electrode was formed in aplating solution initially comprising 1.0 M sulfuric acid, 0.28 M coppersulfate, 0.23 M stannous sulfate, 0.21 cobalt sulfate, and 200 ppm ofcitric acid. A columnar copper-tin-cobalt structure was deposited at acurrent density of about 0.25 A/cm². Three dimensional copper-tin-cobaltporous dendritic structures were deposited on the columnarcopper-tin-cobalt structure at a current density of about 2.0 A/cm². Theprocess was performed at room temperature.

Example #13

A substrate comprising a titanium layer was placed in an electroplatingchamber comprising a Pt(Ti) anode with a surface area of about 1 m². Athree dimensional copper-tin-cobalt porous electrode was formed in aplating solution initially comprising 1.0 M sulfuric acid, 0.28 M coppersulfate, 0.23 M stannous sulfate, 0.20 cobalt sulfate, and 200 ppm ofcitric acid. A columnar copper-tin-cobalt structure was deposited at acurrent density of about 0.30 A/cm². Three dimensional copper-tin-cobaltporous dendritic structures were deposited on the columnarcopper-tin-cobalt structure at a current density of about 2.0 A/cm². Theprocess was performed at room temperature.

Processing System:

FIG. 4A schematically illustrates a plating system 400 using on whichthe embodiments described herein may be practiced. The plating system400 generally comprises a plurality of processing chambers arranged in aline, each configured to perform one processing step to a substrateformed on one portion of a continuous flexible base 410.

The plating system 400 comprises a pre-wetting chamber 401 configured topre-wet a portion of the flexible base 410.

The plating system 400 further comprises a first plating chamber 402configured to perform a first plating process the portion of theflexible base 410 after being pre-wetted. The first plating chamber 402is generally disposed next to the cleaning pre-wetting station. In oneembodiment, the first plating process may be plating a columnar copperlayer on a seed layer formed on the portion of the flexible base 410.

The plating system 400 further comprises a second plating chamber 403disposed next to the first plating chamber 402. The second platingchamber 403 is configured to perform a second plating process. In oneembodiment, the second plating process is forming a copper or alloy suchas copper-tin porous dendritic structure on the columnar copper layer.

The plating system 400 further comprises a rinsing station 404 disposednext to the second plating chamber 403 and configured to rinse andremove any residual plating solution from the portion of flexible base410 processed by the second plating chamber 403.

The plating system 400 further comprises a third plating chamber 405disposed next to the rinsing station 404. The third plating chamber 405is configured to perform a third plating process. In one embodiment, thethird plating process is forming a thin film over the porous layer. Inone embodiment, the thin film is a tin layer.

The plating system 400 further comprises a rinse-dry station 406disposed next to the third plating chamber 405 and configured to rinseand dry the portion of flexible base 410 after the plating processes. Inone embodiment, the rinse-dry station 406 may comprise one or more vaporjets 406 a configured to direct a drying vapor toward the flexible base410 as the flexible base 410 exits the rinse-dry chamber 406.

The processing chambers 401-406 are generally arranged along a line sothat portions of the flexible base 410 can be streamlined through eachchamber through feed rolls 407 ₁₋₆ and take up rolls 408 ₁₋₆ of eachchamber. In one embodiment, the feed rolls 407 ₁₋₆ and take up rolls 408₁₋₆ may be activated simultaneously during substrate transferring stepto move each portion of the flexible base 410 one chamber forward. Otherdetails of the plating system are disclosed in U.S. Ser. No. 61/117,535,titled APPARATUS AND METHOD FOR FORMING 3D NANOSTRUCTURE ELECTRODE OF ANELECTROCHEMICAL BATTERY AND CAPACITOR, to Lopatin et al., filed Nov. 18,2009, of which FIGS. 5A-5C, 6A-6E, 7A-7C, and 8A-8D and textcorresponding to the aforementioned figures are incorporated byreference.

FIG. 4B schematically illustrates one embodiment of a verticalprocessing system 420 according to embodiments described herein. Theprocessing system 420 generally comprises a plurality of processingchambers 432-454 arranged in a line, each configured to perform oneprocessing step to a vertically positioned flexible conductive substrate430. In one embodiment, the processing chambers 432-454 are stand alonemodular processing chambers wherein each modular processing chamber isstructurally separated from the other modular processing chambers.Therefore, each of the stand alone modular processing chambers, can bearranged, rearranged, replaced, or maintained independently withoutaffecting each other. In one embodiment, the vertical processing chamberis configured to perform a dual-sided deposition process, e.g.,simultaneously process opposite sides of the flexible conductivesubstrate. Exemplary embodiments of the processing chambers aredisclosed in U.S. patent application Ser. No. 11/566,202, titledHIGH-ASPECT RATIO ANODE AND APPARATUS FOR HIGH-SPEED ELECTROPLATING ON ASOLAR CELL SUBSTRATE, to Lopatin et al., filed Dec. 1, 2006, which ishereby incorporated by reference in its entirety.

In one embodiment, the processing system 420 comprises a first platingchamber 432 configured to perform a first plating process, for aexample, a copper plating process, on at least a portion of the flexibleconductive substrate 430. In one embodiment, the first plating chamber432 is adapted to plate a copper conductive microstructure over thevertically oriented conductive flexible substrate 430. In oneembodiment, the copper conductive microstructure comprises a columnarmetal layer with a porous conductive dendritic structure depositedthereon.

In one embodiment, the processing system 420 further comprises a firstrinse chamber 434 configured to rinse and remove any residual platingsolution from the portion of the vertically oriented conductive flexiblesubstrate 430 with a rinsing fluid, for example, de-ionized water, afterthe first plating process.

In one embodiment, the processing system 420 further comprises a secondplating chamber 436 disposed next to the first rinse chamber 434. In oneembodiment, the second plating chamber 436 is configured to perform asecond plating process. In one embodiment, the second plating chamber436 is adapted to deposit a second conductive material, for example,tin, over the vertically oriented conductive flexible substrate 430.

In one embodiment, the processing system 420 further comprises a secondrinse chamber 438 configured to rinse and remove any residual platingsolution from the portion of the vertically oriented conductive flexiblesubstrate 430 with a rinsing fluid, for example, de-ionized water, afterthe second plating process. In one embodiment, a chamber 440 comprisingan air-knife is positioned adjacent to the second rinse chamber 438.

In one embodiment, the processing system 420 further comprises a firstspray coating chamber 442 configured to deposit a powder over and/orinto the conductive microstructure on the vertically oriented conductivesubstrate 430. Although discussed as a spray coating chamber, the firstspray coating chamber 442 may be configured to perform any of theaforementioned powder deposition processes.

In one embodiment, the processing system 420 further comprises anannealing chamber 444 disposed adjacent to the first spray coatingchamber 442 configured to expose the vertically oriented conductivesubstrate 430 to an annealing process. In one embodiment, the annealingchamber 444 is configured to perform a drying process such as a rapidthermal annealing process.

In one embodiment, the processing system 420 further comprises a secondspray coating chamber 446 positioned adjacent to the annealing chamber444. Although discussed as a spray coating chamber, the second spraycoating chamber 446 may be configured to perform any of theaforementioned powder deposition processes. In one embodiment, thesecond spray coating chamber is configured to deposit an additivematerial such as a binder over the vertically oriented conductivesubstrate 430. In embodiments where a two pass spray coating process isused, the first spray coating chamber 442 may be configured to depositpowder over the vertically oriented conductive substrate 430 during afirst pass using, for example, an electrostatic spraying process, andthe second spray coating chamber 446 may be configured to deposit powderover the vertically oriented conductive substrate 430 in a second passusing, for example, a slit coating process.

In one embodiment, the processing system 420 further comprises a firstdrying chamber 448 disposed adjacent to the second spray coating chamber446 configured to expose the vertically oriented conductive substrate430 to a drying process. In one embodiment, the first drying chamber 448is configured to perform a drying process such as an air drying process,an infrared drying process, or a marangoni drying process.

In one embodiment, the processing system 420 further comprises acompression chamber 450 disposed adjacent to the first drying chamber448 configured to expose the vertically oriented conductive substrate430 to a calendaring process to compress the deposited powder into theconductive microstructure.

In one embodiment, the processing system 420 further comprises a thirdspray coating chamber 452 positioned adjacent to the compression chamber450. Although discussed as a spray coating chamber, the third spraycoating chamber 452 may be configured to perform any of theaforementioned powder deposition processes. In one embodiment, the thirdspray coating chamber 452 is configured to deposit a separator layerover the vertically oriented conductive substrate.

In one embodiment, the processing system 420 further comprises a seconddrying chamber 454 disposed adjacent to the third spray coating chamber452 configured to expose the vertically oriented conductive substrate430 to a drying process. In one embodiment, the second drying chamber454 is configured to perform a drying process such as an air dryingprocess, an infrared drying process, or a marangoni drying process.

In certain embodiments, the processing system 420 further comprisesadditional processing chambers. The additional modular processingchambers may comprise one or more processing chambers selected from thegroup of processing chambers comprising an electrochemical platingchamber, an electroless deposition chamber, a chemical vapor depositionchamber, a plasma enhanced chemical vapor deposition chamber, an atomiclayer deposition chamber, a rinse chamber, an anneal chamber, a dryingchamber, a spray coating chamber, and combinations thereof. It shouldalso be understood that additional chambers or fewer chambers may beincluded in the in-line processing system.

The processing chambers 432-454 are generally arranged along a line sothat portions of the vertically oriented conductive substrate 430 can bestreamlined through each chamber through feed roll 460 and take up roll462.

In embodiments where a cathode structure is formed, chamber 432 may bereplaced with a chamber configured to perform aluminum oxide removal andchamber 436 may be replaced with an aluminum electro-etch chamber.

Rather then using roughened copper as a base for the active anodicmaterial, research is being done on using copper dendrites. We believethis to be the most promising solution.

To grow the dendrites, a technique called electrochemical deposition isused. This process involves immersing a smooth substrate, such as acopper substrate, in a sulfuric acid bath, wherein a potential willeventually be established. The electric potential spike at the anode isgreat enough that reduction reactions occur. Hydrogen gas bubbles formas a byproduct of the reduction reactions. At the same time, dendritesare constantly being created from Cu grains in the electrolyte.Dendrites end up growing around these bubbles because there is noelectrolyte-electrode contact underneath the bubble. In a way, thesemicroscopic bubbles serve as templates for dendritic growth. This is whythese anodes have many spherical pores.

As the bubbles rise, they may combine with nearby bubbles (known ascoalescence), to form larger dendrite templates. The artifacts remainingfrom this entire process are (relatively) large pores in the dendriticgrowth. With the goal of maximizing surface area, it is preferable tominimize the size of these pores. The most intuitive approach involvesminimizing bubble coalescence. To do this, the voltage spike isintroduced more gradually, as to produce the same amount of sulfuricacid reduction over a longer period of time. When this approach istaken, and the bubble population density is lower because the reductionrate is lower. If the bubble density is lower, less coalescence occursand the bubbles stay smaller. This has the effect of exposing thedendrite growths to smaller bubble templates, thereby leaving smallerpores on the sample.

Results:

FIG. 5 is a representation of a scanning electron microscope (SEM) imageof a three dimensionally plated electrode deposited according toembodiments described herein. The SEM image was taken at 655× at a 36degree tile with respect to the lens, trigonometric tilt correctionapplied. The copper dendrite or “tree” structure was deposited using theelectrochemical deposition techniques described herein. The copperdendrite structure is electrically coupled with the substrate resultingin very low resistance from the bottom of the copper tree structure tothe top of the structure.

FIG. 6 is a representation of a SEM image of a three dimensionallyplated electrode deposited according to embodiments described herein.FIG. 6 depicts a schematic representation of tin nano-rod arrays. TheSEM image was taken at 201× at a 36 degree tilt with respect to thelens, trigonometric tilt correction applied. The nano-rods are connectedto each other and to the substrate thus offering very low resistance.

FIGS. 7A-7D are schematic representations of SEM images of threedimensionally plated electrodes deposited according to embodimentsdescribed herein. FIG. 7A is a representation of three dimensionalcopper-tin plated on copper foil. The SEM image was taken at 23× at a 36degree tilt with respect to the lens, trigonometric tilt correctionapplied. FIG. 7B is another representation of three dimensionalcopper-tin plated on copper foil. The SEM image was taken at 38× at a 36degree tilt with respect to the lens, trigonometric tilt correctionapplied. FIG. 7C is another representation of three dimensionalcopper-tin plated on copper foil. The SEM image was taken at 100× at a36 degree tilt angle with respect to the lens, trigonometric tiltcorrection applied. FIG. 7D is yet another representation of copper-tinplated on copper foil. The SEM image was taken at 37× at a 36 degreetilt angle with respect to the lens, trigonometric tilt correctionapplied.

FIG. 8 is an XRD spectra of plated copper-tin plated according toembodiments described herein and a copper-tin phase diagram. The XRDspectra indicate the presence of Cu₆Sn₅ which is the preferred mediumfor lithium ion absorbing medium.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

The invention claimed is:
 1. A battery, comprising: a flexibleconductive current collector having a smooth surface; a porous electrodecomprising: a columnar metal layer formed on the smooth surface of theflexible conductive current collector; a three-dimensional metalmacro-porous dendritic structure formed over the columnar metal layer,wherein the three-dimensional metal macro-porous dendritic structure haspores of about 100 microns or less; and a tin layer formed on thethree-dimensional metal macro-porous dendritic structure; and aseparator formed over the tin layer formed on the three-dimensionalmetal macro-porous dendritic structure, wherein the three-dimensionalmetal macro-porous dendritic structure comprises copper.
 2. The batteryof claim 1, wherein the three-dimensional metal macro-porous dendriticstructure has pores between about 2 nanometers and about 50 nanometers.3. The battery of claim 2, wherein the three-dimensional metalmacro-porous dendritic structure further comprises a tin.
 4. The batteryof claim 1, wherein the columnar metal layer comprises copper and thecolumnar metal layer and the three-dimensional metal macro-porousdendritic structure further comprise one or more metals selected from agroup consisting of: cobalt, tin, titanium, alloys thereof, andcombinations thereof.
 5. The battery of claim 1, wherein the flexibleconductive current collector comprises a material selected from thegroup consisting of: copper, aluminum, nickel, zinc, tin, stainlesssteel, and combinations thereof.
 6. The battery of claim 1, wherein thecolumns of the columnar metal layer comprise dendritic material.
 7. Thebattery of claim 1, wherein the separator is a porous separator.
 8. Thebattery of claim 7, wherein the separator comprises a material selectedfrom the group consisting of: polyolefin, polypropylene, polyethylene,and combinations thereof.
 9. The battery of claim 8, wherein theseparator further comprises inorganic particles selected from the groupconsisting of: aluminum oxide, silica, ceramic particles, andcombinations thereof embedded in the separator.
 10. A battery,comprising: a flexible conductive current collector having a smoothsurface; a porous anode structure comprising: a columnar metal layerformed on the smooth surface of the flexible conductive currentcollector; a three-dimensional metal macro-porous dendritic structureformed over the columnar metal layer, wherein the three-dimensionalmetal macro-porous dendritic structure has pores of about 100 microns orless; and a tin layer formed on the three-dimensional metal macro-porousdendritic structure; a separator formed over the tin layer formed on thethree-dimensional metal macro-porous dendritic structure; and a cathodestructure, wherein the three-dimensional metal macro-porous dendriticstructure comprises copper.
 11. The battery of claim 10, wherein thethree-dimensional metal macro-porous dendritic structure has poresbetween about 2 nanometers and about 50 nanometers.
 12. The battery ofclaim 11, wherein the three-dimensional metal macro-porous dendriticstructure further comprises a tin.
 13. The battery of claim 10, whereinthe columnar metal layer comprises copper and the columnar metal layerand the three-dimensional metal macro-porous dendritic structure furthercomprise one or more metals selected from a group consisting of: cobalt,tin, titanium, alloys thereof, and combinations thereof.
 14. The batteryof claim 10, wherein the flexible conductive current collector comprisesa material selected from the group consisting of: copper, aluminum,nickel, zinc, tin, stainless steel, and combinations thereof.
 15. Thebattery of claim 10, wherein the columns of the columnar metal layercomprise dendritic material.
 16. A battery, comprising: a flexibleconductive current collector having a smooth surface; a barrier layerformed on the conductive current collector; a porous electrodecomprising: a columnar metal layer formed on the barrier layer; athree-dimensional metal macro-porous dendritic structure formed over thecolumnar metal layer, wherein the three-dimensional metal macro-porousdendritic structure has pores of about 100 microns or less; and a tinlayer formed on the three-dimensional metal macro-porous dendriticstructure; and a separator formed over the tin layer formed on thethree-dimensional metal macro-porous dendritic structure, wherein thecolumnar metal layer and the three-dimensional metal macro-porousdendritic structure comprise copper.
 17. The battery of claim 16,wherein the columnar metal layer and the three-dimensional metalmacro-porous dendritic structure further comprise a metal selected froma group consisting of cobalt, tin, titanium and combinations thereof.18. The battery of claim 16, wherein the three-dimensional metalmacro-porous dendritic structure has pores between about 2 nanometersand about 50 nanometers.
 19. The battery of claim 16, wherein thecolumns of the columnar metal layer comprise dendritic material.
 20. Thebattery of claim 16, wherein the barrier layer is selected from thegroup consisting of chromium, tantalum (Ta), tantalum nitride (TaN),titanium (Ti), titanium nitride (TiN), tungsten (W), tungsten nitride(WN), and combinations thereof.